JWKS Rotation - OpenID Connect Authentication
Key rotation is when a key is retired and replaced by generating a new cryptographic key. Rotating keys on a regular basis is an industry standard and follows cryptographic best practices.
You can manually rotate keys periodically to change the JSON web key (JWK) key, or you can configure the appropriate schedule in CAS configuration so it would automatically rotate keys for you.
Rotation GuidanceNIST guidelines seem to recommend a rotation schedule of at least once every two years. In practice, modest CAS deployments in size and scale tend to rotate keys once every six months, either manually or automatically on a schedule.
Keys that are generated by CAS and put into the keystore carry an extra state parameter that indicates
the lifecycle status of the assigned key. The following values are accepted lifecycle states:
| Value | Description |
|---|---|
0 |
The key is active and current, used for required operations. |
1 |
The key will be the next key used during key rotation. |
2 |
The key is no longer used and active, and will be removed after revocation operations. |
CAS always signs with only one signing key at a time, typically the very first key listed and loaded from the keystore,
that is deemed active and current judging by the state parameter. For backward compatibility, the absence of this
parameter indicates that the key is active and current.
The dynamic discovery endpoint will always include both the current key and the next key, and it may also include the previous key(s) if the previous key has not yet been revoked. To provide a seamless experience in case of an emergency, client applications should be able to use any of the keys specified in the discovery document.
The following settings and properties are available from the CAS configuration catalog:
cas.authn.oidc.jwks.revocation.schedule.cron-expressionA cron-like expression, extending the usual UN*X definition to include triggers on the second, minute, hour, day of month, month, and day of week.
A cron-like expression, extending the usual UN*X definition to include triggers on the second, minute, hour, day of month, month, and day of week. For example, 0 * * * * MON-FRI means once per minute on weekdays (at the top of the minute - the 0th second) or 0 0 0 * * * means every day at midnight. * Note that when cron expressions are defined, the start delay and repeat interval settings are must be removed and set to blank.
cas.authn.oidc.jwks.revocation.schedule.cron-time-zoneA time zone for which the cron expression will be resolved.
A time zone for which the cron expression will be resolved. By default, this attribute is empty (i.e. the scheduler's time zone will be used).
cas.authn.oidc.jwks.revocation.schedule.enabledWhether scheduler should be enabled to schedule the job to run.
trueWhether scheduler should be enabled to schedule the job to run.
cas.authn.oidc.jwks.revocation.schedule.enabled-on-hostOverrides SchedulingProperties#enabled property value of true if this property does not match hostname of CAS server.
.*Overrides SchedulingProperties#enabled property value of true if this property does not match hostname of CAS server. This can be useful if deploying CAS with an image in a statefulset where all names are predictable but where having different configurations for different servers is hard. The value can be an exact hostname or a regular expression that will be used to match the hostname.
cas.authn.oidc.jwks.revocation.schedule.repeat-intervalString representation of a repeat interval of re-loading data for a data store implementation.
PT2MString representation of a repeat interval of re-loading data for a data store implementation. This is the timeout between consecutive job’s executions.
cas.authn.oidc.jwks.revocation.schedule.start-delayString representation of a start delay of loading data for a data store implementation.
PT15SString representation of a start delay of loading data for a data store implementation. This is the delay between scheduler startup and first job’s execution
cas.authn.oidc.jwks.rotation.schedule.cron-expressionA cron-like expression, extending the usual UN*X definition to include triggers on the second, minute, hour, day of month, month, and day of week.
A cron-like expression, extending the usual UN*X definition to include triggers on the second, minute, hour, day of month, month, and day of week. For example, 0 * * * * MON-FRI means once per minute on weekdays (at the top of the minute - the 0th second) or 0 0 0 * * * means every day at midnight. * Note that when cron expressions are defined, the start delay and repeat interval settings are must be removed and set to blank.
cas.authn.oidc.jwks.rotation.schedule.cron-time-zoneA time zone for which the cron expression will be resolved.
A time zone for which the cron expression will be resolved. By default, this attribute is empty (i.e. the scheduler's time zone will be used).
cas.authn.oidc.jwks.rotation.schedule.enabledWhether scheduler should be enabled to schedule the job to run.
trueWhether scheduler should be enabled to schedule the job to run.
cas.authn.oidc.jwks.rotation.schedule.enabled-on-hostOverrides SchedulingProperties#enabled property value of true if this property does not match hostname of CAS server.
.*Overrides SchedulingProperties#enabled property value of true if this property does not match hostname of CAS server. This can be useful if deploying CAS with an image in a statefulset where all names are predictable but where having different configurations for different servers is hard. The value can be an exact hostname or a regular expression that will be used to match the hostname.
cas.authn.oidc.jwks.rotation.schedule.repeat-intervalString representation of a repeat interval of re-loading data for a data store implementation.
PT2MString representation of a repeat interval of re-loading data for a data store implementation. This is the timeout between consecutive job’s executions.
cas.authn.oidc.jwks.rotation.schedule.start-delayString representation of a start delay of loading data for a data store implementation.
PT15SString representation of a start delay of loading data for a data store implementation. This is the delay between scheduler startup and first job’s execution
Required settings may be needed to activate or affect the feature; review them even when they have a default. Optional settings only need to be set to change a default or to turn on the behavior they control. Third party settings belong to libraries such as Spring Boot that CAS builds on; their own documentation may have more detail.
Notes on configuration
Configuration Metadata
The collection of configuration properties listed in this section are automatically generated from the CAS source and components that contain the actual field definitions, types, descriptions, modules, etc. This metadata may not always be 100% accurate, or could be lacking details and sufficient explanations.
Be Selective
This section is meant as a guide only. Do NOT copy/paste the entire collection of settings into your CAS configuration; rather pick only the properties that you need. Do NOT enable settings unless you are certain of their purpose and do NOT copy settings into your configuration only to keep them as reference. All these ideas lead to upgrade headaches, maintenance nightmares and premature aging.
YAGNI
Note that for nearly ALL use cases, declaring and configuring properties listed here is sufficient. You should NOT have to explicitly massage a CAS XML/Java/etc configuration file to design an authentication handler, create attribute release policies, etc. CAS at runtime will auto-configure all required changes for you. If you are unsure about the meaning of a given CAS setting, do NOT turn it on without hesitation. Review the codebase or better yet, ask questions to clarify the intended behavior.
Naming Convention
Property names can be specified in very relaxed terms. For instance cas.someProperty, cas.some-property, cas.some_property are all valid names. While all
forms are accepted by CAS, there are certain components (in CAS and other frameworks used) whose activation at runtime is conditional on a property value, where
this property is required to have been specified in CAS configuration using kebab case. This is both true for properties that are owned by CAS as well as those
that might be presented to the system via an external library or framework such as Spring Boot, etc.
Note
When possible, properties should be stored in lower-case kebab format, such as cas.property-name=value.
The only possible exception to this rule is when naming actuator endpoints; The name of the
actuator endpoints (i.e. ssoSessions) MUST remain in camelCase mode.
Settings and properties that are controlled by the CAS platform directly always begin with the prefix cas. All other settings are controlled and provided
to CAS via other underlying frameworks and may have their own schemas and syntax. BE CAREFUL with
the distinction. Unrecognized properties are rejected by CAS and/or frameworks upon which CAS depends. This means if you somehow misspell a property definition
or fail to adhere to the dot-notation syntax and such, your setting is entirely refused by CAS and likely the feature it controls will never be activated in the
way you intend.
Validation
Configuration properties are automatically validated on CAS startup to report issues with configuration binding, especially if defined CAS settings cannot be recognized or validated by the configuration schema. Additional validation processes are also handled via Configuration Metadata and property migrations applied automatically on startup by Spring Boot and family.
Indexed Settings
CAS settings able to accept multiple values are typically documented with an index, such as cas.some.setting[0]=value. The index [0] is meant to be
incremented by the adopter to allow for distinct multiple configuration blocks.
Custom
It is possible to design and inject your own key rotation and revocation
strategy into CAS using the following @Bean that would be registered in a @AutoConfiguration class:
1
2
3
4
@Bean
public OidcJsonWebKeystoreRotationService oidcJsonWebKeystoreRotationService() {
return new MyJsonWebKeystoreRotationService();
}
Your configuration class needs to be registered with CAS. See this guide for better details.